Temporal variation in soil carbon in various paddy soil types in a cold temperate continental monsoon climate

Abstract Soil organic carbon (SOC) is the most important carbon pool in the terrestrial ecosystem. However, temporal variations in paddy SOC under a temperate continental monsoon climate are poorly understood. Here, we demonstrate that significant SOC variations occur in meadow soil (MS), black soil (BS) and planosol (PS) paddy soils. Several soil samples were collected from different regions where rice was cultivated for 1, 6, 10, 23 and 40 years for MS samples; for 1, 6, 10, 20 and 35 years for BS samples and 1, 5, 10, 15 and 25 years for PS samples. The total organic carbon (TOC) content and humus organic carbon (HOC) content were found to increase as the rice cultivation duration increased, while the mineralizable organic carbon (MOC) content and carbohydrate organic carbon (COC) content exhibited the opposite trend. The relationships between the relative carbon accumulation (Y) in the three soil types and time (X) were consistent with the following models: Y TOC = 0.9973X 0.0245 , Y HOC = 0.9936X 0.0457 , Y MOC = 1.023X −0.073 , and Y COC = 1.040X −0.059 , describing the temporal variation in the various forms of organic carbon in paddy soils under a temperate continental monsoon climate. The results of this study provide a reference for soil carbon pool management and fertilization management.